RE: Multi-Threaded fork() correctness on Linux 2.4 & 2.6

[Linus Torvalds <torvalds@osdl.org>]

On Mon, 19 Sep 2005, Smarduch Mario-CMS063 wrote:
>
> But I don't see the samething in 2.4.31 (which what we're using now).

I'm pretty sure 2.4.x should have the mmap_sem too.

But I think there it's aquired by the caller of dup_mmap() (ie it's 
"copy_mm()" that gets the mmap_sem and holds it for the duration of 
dup_mmap).

In fact, I'm sure: the mmap_sem was changed from a regular semaphore to a
read-write semaphore in 2.4.2.5, and we definitely took it around
dup_mmap() at that point. 

Of course, maybe some broken change removed it later in 2.4.x, I don't 
keep a current 2.4.x tree around.

		Linus
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